In many applications in oil or gas wells, a main tubular conduit, such as production tubing, is run into the wellbore with a bottom hole assembly attached. The bottom hole assembly may have a wireline, control line, vent line, or other such longitudinal member(s) attached to it. Typically, these wireline, control line, vent line, or other such longitudinal member(s) will be run externally to the production tubing. Such longitudinal members will be referred to as external longitudinal members herein. Often, there may be several such external longitudinal members run into the wellbore along with, and external to, the production tubing or other main tubular conduit.
In some circumstances, it becomes necessary to cut or sever the main tubular conduit at a point downhole, and to pull the tubular conduit back out of the hole, leaving the severed lower portion of tubular conduit, and the bottom hole assembly attached thereto, in the wellbore. This also necessitates the cutting of the external longitudinal members, preferably without a separate operation for running specialized cutting equipment into the wellbore. It is also desirable to be able to cut the wireline, control line, vent line, or other such longitudinal member(s) somewhere downhole as close as possible to the point at which the tubular conduit is cut, to salvage as much as possible of the external longitudinal member and keep the wellbore as open as possible.
A prior design described in U.S. Pat. No. 6,997,262 provided a method and apparatus for severing one or more external longitudinal members, with a cutting tool attached to the main tubular conduit, above the bottom hole assembly. The cutting tool consisted of a cutter body which was clamped in place on the external surface of the main tubular conduit, such as by capturing the cutter body between two couplers threaded onto the tubular conduit. Inside the cutter body are cutter knives which slide longitudinally relative to the cutter body. These cutter knives are fixedly attached to the external longitudinal member, such as by being clamped thereto. The external longitudinal member or members are routed through the cutter body so as to be exposed to the cutting edge of the knife or knives. If there are several knives, they can be oriented facing each other, and the external longitudinal member or members are routed between the cutting edges on the cutter knives. A surface on each cutter knife abuts an actuating surface on the cutter body, with this actuating surface sloping downwardly and transversely to the longitudinal axis of the cutting tool. If there are several cutter knives, there can be a single conical actuating surface, or several actuating surfaces.
If it became necessary to sever the main tubular conduit and retrieve the upper portion, this operation was first accomplished below the cutting tool. The upper portion of the tubular conduit is then pulled upwardly, or uphole, to retrieve it from the well.
After the tubular conduit is severed, pulling upwardly on the tubular conduit will also lift the cutter body upwardly, or in an uphole direction. At the same time, the external longitudinal member to which the cutter knives are attached is still attached to the bottom hole assembly, thereby holding the cutter knives in place longitudinally in the well bore. The uphole movement of the cutter body relative to the cutter knives caused the sloping actuating surfaces on the cutter body to engage the abutting surfaces on the cutter knives and forced the cutter knives toward each other, or inwardly. This drove the cutting edges of the cutter knives through the external longitudinal member or members, severing them. This allowed the external longitudinal member or members and the cutting tool to be simultaneously retrieved from the well bore.
As shown in FIG. 1, a preferred embodiment of the apparatus 10 includes generally a cutter body 12, and one or more cutter knives 18,20. The cutter body 12 has a longitudinal bore 14 therethrough, for passage of a tubular conduit TC to which the apparatus 10 of the present invention may be attached. For example, the cutter body 12 can be captured in place longitudinally on the tubular conduit TC by threading of couplers (not shown), as is known in the art, on the ends of the section of tubular conduit TC, above and below the cutter body 12.
The cutter body 12 has a generally longitudinal knife chamber 16 in which the cutter knives 18, 20 are slidably positioned. The cutter knives 18, 20 have clamping bodies 22, 24 near their upper ends. The clamping bodies 22, 24 can be fastened together, as shown better in FIG. 2, to clamp tightly around a longitudinal member, such as a wireline WL, which is positioned externally to the tubular conduit TC. The clamping bodies 22, 24 can be bolted together at mating surfaces 50, as is well known in the art. The bolts and bolt holes are omitted in these views, for the sake of clarity.
The cutter knives 18, 20 have thinner mid-sections 26, 28, which can flex to allow the lower ends of the knives 18, 20 to deflect inwardly, as will be explained below. Cutter blades 30, 32 are mounted on the knives 18, 20 near their lower ends, with the blades 30, 32 having cutting edges 34, 36 facing each other, or facing inwardly. FIG. 3 shows this orientation of the cutting edges 34, 36. Stiffeners 52, 54 can be provided on the cutter knives 18, 20 if required.
As seen in FIGS. 1 through 3, a wireline passage 38 is provided longitudinally through the cutter body 12, as is a vent line passage 40. Similarly, a passage could be provided for a control line or any other kind of external longitudinal member that may be in use next to the tubular conduit TC. These longitudinal member passages, 38 and 40, position the external longitudinal members VL, WL between the cutter knives 18, 20, and specifically between the cutting edges 34, 36. As shown in FIG. 3, one cutting edge 36 can be V-shaped to centralize the vent line VL and the wireline WL between the cutting edges 34, 36.
A set of teeth or serrations 42 can be provided within the wireline passage 38, to facilitate holding the cutter knives 18, 20 in position longitudinally relative to the wireline WL, when the clamping bodies 22, 24 are bolted together. The portion of the wireline passage 38 between the clamping bodies 22, 24 is dimensioned to slightly squeeze the wireline WL, without collapsing it or otherwise damaging it. The vent line passage 40 is dimensioned to allow passage of the vent line VL without squeezing it. As shown in FIG. 2, bolts and bolt holes 44 are provided to bolt together the two halves 12A, 12B of the cutter body 12, in a similar fashion to that contemplated for the clamping bodies 22, 24. Bolting together of the two cutter body halves 12A, 12B facilitates positioning of the cutter knives 18, 20 within the knife chamber 16.
As shown best in FIG. 1, one or more sloping surfaces 46,48 are provided at the lower end of the knife chamber 16, sloping longitudinally and inwardly toward the longitudinal members VL,WL passing through the cutter body 12. The lower ends of the cutter knives 18, 20 abut these sloping surfaces 46, 48. Rather than having two distinct sloping surfaces, a conical sloping surface could be used with a plurality of inwardly facing knives.
The configurations shown in FIGS. 1 and 3 represent the made-up or run-in configuration of the apparatus 10. After the tubular conduit TC and the bottom hole assembly (not shown) are positioned in the wellbore, it may become necessary to sever the tubular conduit TC, the vent line VL, and the wireline WL above the bottom hole assembly and retrieve them from the wellbore. After the tubular conduit TC is severed, by any means known in the art, the upper portion of the tubular conduit TC is pulled upwardly, or in the uphole direction.
As shown in FIG. 4, this lifts the cutter body 12 in the uphole direction. Since the cutter knives 18, 20 are clamped in position longitudinally on the wireline WL, the lower end of which is still attached to the bottom hole assembly, the cutter knives 18, 20 are forced inwardly by the sloping surfaces 46, 48 in the cutter body 12, as the cutter body 12 rises. This forces the cutting edges 34, 36 of the blades 30, 32 toward each other, through the longitudinal members VL, WL, severing them. FIG. 5 shows the overlapping of the cutter blades 30, 32 after the cutter knives 18, 20 have been forced fully inwardly by the sloping surfaces 46, 48. After the severing operation, the upper portions of the external longitudinal members VL, WL can be retrieved from the wellbore.
There were two main issues with the technique described above and the associated FIGS. One issue was the need to run a line cutter into the string to cut it as the preferred technique to sever a portion of the string from the bottom hole assembly (BHA). This added time, cost, and risk to the operation. Apart from this, was that after the string was cut and picked up and the members VL and WL were cut, what remained below the cut location fell into the well and made subsequent fishing operations more difficult, if not impossible, by getting in the way of the retrieving or fishing tools.
The present invention addresses these problem areas in the prior design. It uses a breakaway coupling that comes apart by a tensile force on the string to part the string. Having parted the string, the cutter assembly has the housing and cutter location inverted from the previous design. When the string is parted and is pulled up, what happens is that the external longitudinal conduit(s) are tensioned, pulling the knives into the cutting mode, but hanging on to the lower cut portion of the external longitudinal conduit(s) from just below the cut location to the fixation location in the BHA, so that there is no loose end that can fall into the wellbore and disturb subsequent fishing or other operations. Those skilled in the art will better understand the invention from a review of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is given by the appended claims.